Separating Mount Desert Island from the mainland, Mount Desert Narrows (together with Eastern Bay) is a thin strip of saltwater extending from roughly Haynes Point in Trenton in the west to Lamoine Beach in the east. The narrows includes several small islands, coves, and ledges, as well as a small saltmarsh. Thompson Island serves as the gateway to Acadia National Park and endures thousands of visitors annually. The Jordan River, a small estuary, empties into the sea here.
This is an excellent spot for viewing congregations of coastal birds including over 2000 Common Eiders, hundreds of Great Black-backed and Herring Gulls, groups of ducks numbering in the hundreds during all seasons, but especially winter. For many years, this area was known for its wintering population of scaup; one of just a few places to support this species on the entire Maine coast. The narrows supports feeding and roosting habitat for numerous species of shorebirds during fall migration, and three known bald eagle nesting territories are found here.
This site is vulnerable to the same host of threats as other coastal habitats. Overharvesting of prey species, an oil spill, and direct disturbance from commercial fishing as well as disturbance and pollution from shoreline development are chief concerns in this area. Also, disturbance from intense summer recreational use must be considered.
Lands surrounding the Mount Desert Narrows include numerous types of owners. Private commercial and residential developments make up the majority of the owners here. Acadia National Park owns Thompson Island and an adjacent parcel on Mount Desert Island. The Maine Bureau of Parks and Lands operates Lamoine State Park just to the east of the narrows. Some of the best views of the narrows can be made from Thompson Island where there is ample space for parking and picnicking as well as rest room facilities. Two boat launches, one at the Trenton Boat Yard and another at Lamoine State Park, facilitate exploring the narrows from the water without trespassing on private property. A third, more primitive, boat launch can be found on Hadley Point at the north end of Mount Desert Island.